Color imaging systems require filters disposed on matrices of sensors. These filters are typically absorbent filters which transmit one or more defined wavelengths. They are generally fabricated using dyes: the absorption of incident light is performed by the molecules of which the dyes are composed. This procedure for filtering light comprises several drawbacks: the filtering capacity is subject to aging and the materials used are not compatible with methods for fabricating CMOS light sensors.
Abbarchi et al. (Abbarchi, M., Naffouti, M., Vial, B., Benkouider, A., Lermusiaux, L., Favre, L., . . . & Bonod, N., 2014, Wafer Scale Formation of Monocrystalline Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting. ACS nano, 8(11), 11181-11190) have disclosed a procedure for fabricating a filter based on the resonance of semi-conducting nano-/microparticles, making it possible to effectively scatter light incident on the surface of a component by electromagnetic resonance in the material of the nano-/microparticle. Their resonant frequencies depend on the size and on the material used. To produce these resonators, Abbarchi et al. use a silicon on insulator substrate on which a germanium layer can be deposited. Controlled pressure and temperature conditions induce dewetting of the semi-conducting layer(s) on the layer of SiO2. The “droplets” of semi-conductor (silicon and/or germanium) form nano-/microparticles on the surface of the insulator. This procedure exhibits the benefit of being compatible with CMOS fabrication criteria since it does not use, in particular, any metal, in contradistinction to the procedures using microstructures implementing surface plasmons. On the other hand, the disclosed procedure does not make it possible to control a posteriori the resonant frequency of the fabricated nano-/microparticles since the size and the material of these particles are fixed during fabrication.
The invention also relates to a photodetector. Imaging systems generally comprise a matrix of photodetectors, for example of CMOS or p-n junction type, the spectral band of each of whose photodetectors is fixed. Color imaging requires independent detection of several spectral bands: photodetectors of one and the same matrix must then comprise filters of different spectral bands. The photodetectors produced in this manner are not tunable a posteriori and their fabrication requires additional technological steps which are not compatible with CMOS fabrication criteria.